Answer: d [Reason:] The cured urea resins do not impart colour and odour to food and drinks with which they may come in contact. They are hard, rigid and non-inflammable but they char around 200 ᵒC. They exhibit excellent insulation properties.

Answer: a [Reason:] Metal stearate like zinc stearate, aluminium stearate, etc. (quantity about 1%) is used as a lubricant in the moulding powder.

Answer: c [Reason:] To improve the shelf life of moulding powders, it should be stored in cool place. Incorporation of a small amount of a stabilizer such as hexamine further improves shelf-life.

Answer: a [Reason:] Urea is potentially tetrafunctional and the use of 1.5 to 2 moles of formaldehyde for each mole of urea yields useful resins.

Answer: c [Reason:] The adhesive resins are prepared in the water solube form, stabilized by maintaining the pH at 7.5 and a solid content of nearly 50-70%.

Answer: a [Reason:] The resins are hardened under acidic conditions and ammonium chloride is used as most common hardening agent for resins which acts as acid donor.

Answer: b [Reason:] Dicyandiamide is produced by heating cyanamide at a temperature of about 70-80 C.

Answer: a [Reason:] An initial molar ratio of 1:3 for melamine to formaldehyde is used in commercial resinification reactions.

Answer: b [Reason:] The temperatures in the range of 150-170 C and pressure of the order 2000-8000 psi are employed for compression moulding of m-f resins.

Answer: a [Reason:] The exceptional hardness, solvent resistance and heat stability qualities of m-f resin make it suitable to be used as decorative laminates.

Answer: a [Reason:] The electrical grade laminates are produced by using triethanolamine as condensation catalyst rather than sodium carbonate as catalyst. They are usually made by impregnationg electrical-grade glass cloth with the triethanolamine catalyzed resin.

Answer: c [Reason:] The termination reaction in anionic polymerization most probably takes place by the chain transfer involving solvent or some other additive used such as water, alcohol, etc.

Answer: c [Reason:] According to the reactivity order given by Mayo and Walling,
Acrylonitrile>Methacrylonitrile>Methyl methacrylate>butadiene
This order is decided on the basis of the electronegativity of the electron-withdrawing substituent groups.

Answer: a [Reason:] Acidic solvents or additives inhibit the growth in anionic polymerization.

Answer: a [Reason:] The monomers with electron accepting substituent groups like nitrile, carboxyl, ester groups, etc. are readily susceptible to anionic polymerization as the it enables easy carbanion formation.

Answer: b [Reason:] The ease of anionic polymerization is dependent not only on the catalyst system for a given monomer, but also on the structure of the monomer for a given catalyst.

Answer: c [Reason:] The basic compounds like amides, aryls, alkoxides and Grignard reagents (R-MgX) are used as catalysts for anionic polymerization.

Answer: c [Reason:] The effectiveness of the catalyst in the initiation process of anionic polymerization depends on its basicity as well as the acidity of monomer.

Answer: c [Reason:] According to the rate expression for overall rate
R_p α [M]²
So the rate is quadrupled, if the monomer concentration is doubled.

Answer: c [Reason:] Styrene contains the phenyl group which is less electronegative than the nitrile group (-CN) attached to the other three monomers, so it is more susceptible to proton transfer from ammonia. And transfer reactions generally yield low-molecular weight polymers.

Answer: d [Reason:] According to the expression for degree of polymerization,
X_n α [M]/[NH₃]
Since the degree of increase in the concentration of both monomer and liquid ammonia is not known, we cannot determine that whether the degree of polymerization will increase or decrease.

Answer: d [Reason:] Styrene is capable of polymerizing by radical as well as cationic and anionic mechanisms. It is placed at a low position in each series of reactivity.

Answer: a [Reason:] Bimolecular termination is not feasible in the ionic polymerization, as like charges repel each other and cannot come close enough to interact with each other and annihilate together.

Answer: a [Reason:] Basic solvents or additives can inhibit the growth of polymer in cationic polymerization.

Answer: c [Reason:] The reactivity order for cationic polymerization proposed by Mayo and Walling states-
Vinyl ethers>isobutylene>isoprene>styrene.

Answer: b [Reason:] The monomers with electron releasing substituent groups like alkoxy, phenyl, aryl-alkyl, etc. are readily susceptible to cationic polymerization as the it enables easy carbonium formation.

Answer: b [Reason:] Cationic polymerization generally occurs around -100ᵒC temperature. So, the rate and degree of polymerization drops sharply with rise in the temperature.

Answer: a [Reason:] The rate of cationic polymerization is given by-
R_p= (k_ik_p/k_t)[C][M]²
Thus, R_p is proportional to the first power of catalyst concentration.

Answer: a [Reason:] The degree of polymerization for transfer reaction is given is a constant which is given by-
X_n= k_p[M⁺][M]/k_tr[M⁺][M]
X_n= k_p/k_tr
Where k_p and k_tr are propagation and termination constants.

Answer: d [Reason:] The binding energy between the propagating ion and the gegen ion is dependent on the nature of the reaction media and the gegen ion and on the temperature of the reaction.

Answer: a [Reason:] The activation energy for the overall rate is given by [(E_i+E_p)-E_t] and it ranges between -10 to +10 kcal/mol.

Answer: b [Reason:] The activation energy for degree of polymerization is given by (E_p-E_t) and E_t>E_p giving always a negative value. Since E_tr (for transfer reaction) is generally greater than E_t (for true termination), the magnitude of negative activation energy is higher for the termination by transfer reactions than for the true termination.

Answer: a [Reason:] BF₃ is very effective in the presence of traces of moisture as a co-catalyst as it reacts with traces of moisture to form a complex (BF₃∙H₂O) which can readily induce polymerization.

Answer: a [Reason:] The increase in dielectric constant of reaction medium increases the initiation rate constant, k_i by decreasing the energy required for charge separation and simultaneously, it decreases the termination constant, k_t by increasing the energy required for arrangement or combination of ion pair. Since, R_p is directly proportional to the ratio k_i/k_t, an increase in the dielectric constant of reaction medium will increase the rate of reaction.

Answer: a [Reason:] Due to high inflammability and poor chemical and solvent resistance of cellulose nitrate, the use of cellulose nitrate in many areas of application has been considered no suitable. Those areas include photographic films, machine guards, toys, etc. Presently, it finds use in lacquor coatings and printing inks, tool handles, etc.

Answer: b [Reason:] H₂SO₄ is used as a condensing agent. A very low content of water tends to produce high degree of nitration and H₂SO₄ provides that service.

Answer: a [Reason:] Commercial cellulose nitrate used for plastic and coating applications have N₂ content in the range of 10.9-12.2% whereas nitrates with N₂ content greater than 12.5 are used for explosives.

Answer: b [Reason:] Acetic acid acts as a swelling agent for the cellulose and the pretreatment by it, makes cellulose swell whereby it makes accessible to acetic anhydride for acetylation.

Answer: a [Reason:] The primary acetate is soluble in the chlorinated hydrocarbons like chloroform and trichloro ethane while secondary acetate is insoluble in chloroform.

Answer: c [Reason:] Sodium carboxymethyl cellulose of DS in the range of 0.5-1.0 is water soluble and is used in synthetic detergents and as stabilizers and viscosity modifiers in aqueous suspensions and emulsions. Ethyl cellulose is used in hot melt strippable coating formulations and surface coating formulations while methyl cellulose is used as a thickening agent and an emulsifying agent.

Answer: a [Reason:] Soda cellulose is transformed into sodium cellulose xanthate by reacting it with CS₂ i.e. carbon disulphide. The xanthate formed is soluble in dilute aqueous alkali, which on acidification decomposes; the xanthate structure is broken and cellulose is regenerated.

Answer: b [Reason:] The film formed by the viscose solution is known as cellophane and the fibre formed is called viscose rayon. Celluloid is a camphor plasticized product.

Answer: a [Reason:] Cellulose acetate-butyrate is more suitable for producing movie films due its excellent appearance and clarity, toughness and ease of mould ability over cellulose acetate.

Answer: c [Reason:] The effect of chain transfer on R_p depends upon the value of re-initiation constant relative to the value of propagation constant. If k_i^’<< k_p, then chain transfer agent would play the role of an inhibitor or retarder and R_p would be adversely affected.

Answer: a [Reason:] The average degree of polymerization is redefined from the kinetic view point as the ratio of overall rate of polymerization to total rate of production of pairs of chain ends.

Answer: c [Reason:] The chain transfer constant C is defined as the ratio of rate constant, k_tr for chain transfer reaction to the propagation rate constant.

Answer: b [Reason:] In the absence of any solvent in polymerization system, the expression for (1/X_n) is arranged as-
1/X_n = [(y+2)/(y+1)](k_t/k_p²)(R_p/[M]²) + C_M + C_I [I]/[M]
When only monomer transfer takes place, the intercept on 1/X_n axis gives a measure of monomer transfer constant, C_M.

Answer: a [Reason:] The plot of [1/X_n – [(y+2)/(y+1)](k_t/k_p²)(R_p/[M]²)] vs [I]/[M] gives a straight line, whose intercept gives a direct measure of CM and slope gives the value of initiator transfer constant, CI.

Answer: a [Reason:] The reactivity increases with the increasing substitution at the α-carbon, which leads to increasing values of C_S in the order benzene < toluene < ethyl benzene < isopropyl benzene.

Answer: d [Reason:] The other three solvents exhibit high chain transfer activity; they surpass styrene in reactivity towards chain radical and have C_S values greater than unity. Toluene, on the other hand, has a very low C_S value to control the degree of polymerization.

Answer: b [Reason:] The ratio of rate of consumption of the transfer agent and the rate of consumption of monomer can be written as, (d[S]/dt)/(d[M]/dt) = k_tr,S[M]/k_p[S]
= C_S [M]/[S]
d log[M]/d log [S] = C_S
Hence for this system, the linear plot of log [M] against log [S] renders the slope of solvent transfer constant, C_S.

Answer:d [Reason:] The polymer transfer leads to the chain branching which makes it less crystalizable, weak in mechanical properties and less resistant to heat, solvents and chemicals.

Answer: a [Reason:] According to the expression for reciprocal of average degree of polymerization, we have
1/X_n = C_M + (k_t/k_p²)(R_p/[M]²) + C_I(k_t/k_p² fk_d)(R_p²/[M]³)
Comparing the given equation with this one, we get CM as 1.75* 10^-4.

Answer: a [Reason:] According to the expression for reciprocal of average degree of polymerization, we have
1/X_n = C_M + (k_t/k_p²)(R_p/[M]²) + C_I(k_t/k_p² fk_d)(R_p²/[M]³)
Comparing the given equation,
CI(k_t/k_p² fk_d)(R_p²/[M]³) = 1.73*10⁴ R_p²
CI = 1.73*10⁴ * 3.29*10^-9*(8.35)³
CI = 0.035.

Answer: c [Reason:] To decrease molecular weight by 4 times, 1/X_n becomes 4/X_n0,
4/X_n0 = 1/X_n0 + C_I [S]/[M]
Substituting the values, [S]/[M] = 84. Thus, dilution factor is 84.

Answer: b [Reason:] We have the expression for solvent transfer,
1/X_n = 1/X_n0 + C_I [S]/[M]
When molecular weight is halved, 1/X_n becomes 2/X_n0, then substituting the values and [S]/[M]= 7, we get C_I as 0.68.